The objective of this project is the research and development of suitable analytical methods to: (1) establish the structure and purity of potential anti-AIDS agents and new antiviral drugs, (2) determine physical, chemical and biochemical properties, including octanol-water partition coefficients, of these compounds and their metabolites, and (3) measure these drugs and their metabolites in biological samples to elucidate pharmacology and to determine pharmacokinetics. High- performance liquid chromatography and mass spectrometry are emphasized techniques. Compounds of current interest are dideoxynucleosides including 6-halo-dd-Purines, 2-NH2-6-halo-dd-Purines, 2'-F-dd-ara-A, 2'-F-dd-ara-I, 2'-F-dd-ara-G, 2'-F-dd-C, 2'-F2-dd-ara-C and 6-substituted-2'-F-dd-Purines. The role of adenosine deaminase in prodrug activation is under investigation.